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We all love laser guns (which are usually plasma weaponry) but why guns? It's not like we need the long barrel for making it more accurate or the stock to control recoil. So why guns and why not something else?

$\begingroup$Long barrel and stock are parts of rifles. Guns have handle to keep in hand and barrel to aim.$\endgroup$
– SZCZERZO KŁYJan 3 '19 at 14:03

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$\begingroup$Are you asking for (1) justification of the gun shape of the fictional laser gun, or (2) if future handheld laser weapons would actually be gun shaped?$\endgroup$
– Tyler S. LoeperJan 3 '19 at 14:35

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$\begingroup$You need to elaborate more on the question. Pure rhetorical and open questions like this are "too broad". There are dozens of answers and we cannot know which one is a better fit for the question if it is too vague.$\endgroup$
– MindwinJan 3 '19 at 16:50

$\begingroup$@TylerS.Loeper ...or possibly OP is just asking why we use the word "gun" instead of "laser blaster" or some other word. Who knows? The question is vague and poorly defined.$\endgroup$
– J...Jan 3 '19 at 18:32

12 Answers
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User Expectation and Skeumorphic Design

The floppy disk 💾 is used (less so than five years ago, but used) as a save icon, even though outside of old industrial machines and nuclear missile silos, no one uses floppy disks. Your phone makes a shutter sound when you take a picture, despite not having a shutter. Electric cars are designed to look like gasoline vehicles in many ways that are utterly unnecessary, because it’s what people expect, and when something looks the way people expect, it makes them happy and comfortable and more likely to award your Laser Gun Company with the government contract for one million Pew Pew Guns. So your industrial designers make it look like a nice old fashioned projectile-throwing rifle, even if it doesn’t strictly need to.

$\begingroup$I think you hit on the broad psychological phenomenon here. The "gun" is just a literary/theatrical icon for "weapon".$\endgroup$
– elemtilasJan 3 '19 at 19:46

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$\begingroup$But electric cars do share most of the same requirements and limits as any other car, so of course they'll look similar. A hard disk doesn't have the same technical limits of a floppy, so the actual device looks completely different. Skeumorphic design isn't a successful solution in the physical world, and "next generation" devices which use it temporarily are always quickly replaced by designs which use the nature of the new device to do the job better.$\endgroup$
– GrahamJan 4 '19 at 0:51

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$\begingroup$"less so than five years ago" I have literally never seen another icon for save.$\endgroup$
– jpmc26Jan 4 '19 at 2:22

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$\begingroup$I'm suggesting that it's still ubiquitous. Any usages of another icon are rare. "less so" suggests that it's actually starting to decline, but I'm just not convinced that's the case.$\endgroup$
– jpmc26Jan 4 '19 at 2:40

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$\begingroup$On a side note, the shutter sounds prevent someone from sneaking in a photo. It became mandatory in Japan in the early 2000s to curb an upskirt epidemic, so it does serve a function still. The same logic could be applied to gun shapes, to make them recognisable and unable to be passed as something mundane.$\endgroup$
– AmiralPatateJan 4 '19 at 10:50

It's an interesting question because our current laser guns look more like giant flat panels that fire invisible beams of heat at airplanes and torpedoes.

But those are aimed by computers. People need to use sights to aim. A longer barrel gives a more accurate sight and better control of the gun. It also allows the weapon to function like a bat in close fighting and could hold other attachments like grenade launchers or backup conventional rifles for when laser just won't work (like the Chinese mirror armor they developed in response to USA laser weapons).

$\begingroup$It's not about the size of your rail attachment system, it's how you use it!$\endgroup$
– Joe BloggsJan 3 '19 at 14:36

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$\begingroup$The problem is that future warfare with advanced weapons maybe totally computer operated, rather than having stormtroopers running around with blasters.$\endgroup$
– Mark RogersJan 3 '19 at 15:26

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$\begingroup$@AzirisMorora I guess really the gun itself could fire a low power version to function as the targeting before it fires the lethal version.$\endgroup$
– TrevorJan 3 '19 at 15:42

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$\begingroup$@TrevorD This is called laser designation, already used with AN-PEQ attachments and NV google :)$\endgroup$
– Pierre P.Jan 3 '19 at 16:30

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$\begingroup$Ergonomics, +1. I have a ~3" group with pistols at a measly ten feet. Or a ~3" group at 100 yards with a rifle...$\endgroup$
– MazuraJan 4 '19 at 2:22

A laser consists of a gain medium, a mechanism to energize it, and something to provide optical feedback.[8] The gain medium is a material with properties that allow it to amplify light by way of stimulated emission. Light of a specific wavelength that passes through the gain medium is amplified (increases in power).

The accompanying diagram shows that the gain medium is a long tube. The longer the gain medium is, the more the laser is amplified.

Furthermore, one can have a laser version of choke (change the spread of the beam) by having a series of adjustable lenses, and a long barrel facilitates that.

$\begingroup$+1 Stavatti SF-1 Gasdynamic laser rifle (the only realistic design so far AFAIK) has 20in (50cm) chamber alone. The power source is just as big, and the significant recoil makes stacking those the obvious option.$\endgroup$
– Agent_LJan 4 '19 at 11:31

$\begingroup$@Agent_L you mention recoil, and while laser weapons do have recoil, unless you are trying to blow a planet up, I don't think the recoil would be "significant". Am I missing something?$\endgroup$
– Garrett MotznerJan 4 '19 at 22:04

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$\begingroup$The gain depends on the volume, but the length (aspect ratio) of the resonator determines the divergence and that places lower limit on how well the beam can be focused.$\endgroup$
– Jan HudecJan 4 '19 at 23:37

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$\begingroup$@GarrettMotzner In this case, the recoil comes from gas being rushed into the chamber at Mach 6 to power the lasing action (the gasdynamic part). The recoil is forward, opposite of guns. I wholeheartedly recommend reading about SF-1 and TIS-1 whitepaper, because that's fiction transitioning into science in front of us.$\endgroup$
– Agent_LJan 5 '19 at 8:26

$\begingroup$That kind of works, unless you consider that the laser weapon still files straight without a barrel, and there is no need to dissipate heat from a barrel that doesn't exist. So it's kind of a solution to a problem that only exists because of your solution. Also longer would only usefully dissipate heat if the source of the heat was at the tip of the barrel, insulating the user from heat. So yeah longer dissipates heat, but did we need it dissipated from the barrel? I would expect the battery would be the heat problem.$\endgroup$
– TrevorJan 3 '19 at 21:53

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$\begingroup$@TrevorD Industrial lasers need quite a bit of active cooling (and those aren't powerful enough to be useful small arms!). For passive cooling, you need a lot of surface area. It's pretty easy to spread the heat around the heatsink, the throughput limit is on the radiators.$\endgroup$
– LuaanJan 4 '19 at 15:06

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$\begingroup$@Luaan Can you confirm if its the laser creating the heat, or the power source powering the laser?$\endgroup$
– TrevorJan 4 '19 at 15:47

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$\begingroup$@TrevorD With the lasers we have, the power supply is far more efficient than the laser itself. There's losses to the lasing medium, losses to the mirrors, and for microchip lasers, of course the chip gets quite hot (there the heating issue for dangerous laser might be almost insurmountable). In any case, even the heat from the power source needs to be dissipated - and if you use passive cooling, that means lots of radiators. The point is, the barrel is going to be there anyway, and "rifle" (or carabine/SMG) ergonomics are vastly superior to one-handed weapons; gun-shape is smart.$\endgroup$
– LuaanJan 5 '19 at 8:12

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$\begingroup$@Luaan I meant Ray describes the barrel as something that only wraps around the beam, there is no reason for it to be built this way, the barrel should be the part that actually houses the emitter and optics. meaning direct heating by contact with said pieces, just like in normal lasers.$\endgroup$
– JohnJan 5 '19 at 15:15

To aim a weapon accurately, a long barrel is helpful. You also want to have some heft to dampen jitter (Photographers know that a light camera is harder to hold steady).

As well, you need some place to put all of the tech, even if you don't need a long lasing cavity you'll find some use for the volume. A short but thick device would be much less practical, for aiming as well as for carrying.

Of course the validity of all of these reasons depends entirely on the author's whim in a scifi setting. You coud have a short, giro stabilized hand gun with computer assisted aiming and nano components if you so please, but who wants to ruin a good trope?

$\begingroup$Note that your aiming statement assumes "iron sights". Optical sights, such as the current ACOG, can do the job in a much shorter length.$\endgroup$
– WhatRoughBeastJan 3 '19 at 19:40

$\begingroup$hm, maybe optical sights arent such a good idea when your opponents point lasers at you?$\endgroup$
– thsJan 3 '19 at 19:43

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$\begingroup$Well, only for a very particular set of enemy lasers and powers. It would be better only if the optical gain of the optical sight brought enemy emissions over damage thresholds, and most low-power sights don't have all that much gain. Actually, it's perfectly possible to include band-reject filters in optical sights which would make them much safer than using iron sights and Mark I (unprotected) eyeballs.$\endgroup$
– WhatRoughBeastJan 3 '19 at 19:47

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$\begingroup$@WhatRoughBeast: A rifle-like form factor would still help with accuracy in that you have more/cleaner options for resting the firearm on terrain/structures/stands. I'd imagine long-ranger shooters would still prefer something larger than a pistol or TV remote in order to accurately hit targets from afar.$\endgroup$
– EllesedilJan 4 '19 at 17:43

$\begingroup$@WhatRoughBeast ACOG rifles still have iron sights as backup; optical sights can "easily" be thrown out of alignment, and then all you have is an oversized hip-fired SMG :) But anyway, even with optic sights, the ergonomics of the weapon don't really change - you still want something comfortably held in both hands, with one side braced against your shoulder. A HUD (like the Star Wars Stormtroopers have) could make hip-fired weapons reasonably accurate, but that's again something you want a backup for.$\endgroup$
– LuaanJan 5 '19 at 8:32

Some considerations from Atomic Rockets (They have a gorgeous article about side-arms on hard Sci-Fi):

A portable laser weapon can't realisticly exist, since we have a major problem on portability of batteries and to save energy they would need focusing lens what can drive their form to be like a old Super 8 camoder due lens size.

Aiming can be done by a periscope, as in Star Trek, as energy weapons don't have trajectory deformations, like projectiles, reducing the need for a barrel.

$\begingroup$You're not using enough imagination (or reading enough Project Rho :P). A lot of older sci-fi used laser (and other "energy") weapons with battery backpacks. We already have batteries with far higher energy density than you would need for that. Is that a good idea? Of course not, but then again, propelling a deadly projectile with a small explosive isn't exactly sane either :D People do all sorts of ludicrous stuff with severe drawbacks to fight other people. If your magazine is hit with a laser weapon, is it going to go off? Is that much different than the danger posed by laser charges?$\endgroup$
– LuaanJan 5 '19 at 8:26

$\begingroup$Older Sci-Fi had different standards. We don't have any battery close enough energy density and stability to be of practical use, even on a backpack form factor. Of course, we can use a handwavium battery, and use large lens to make this transgression less flagrant.$\endgroup$
– CochiseJan 5 '19 at 9:33

$\begingroup$There are two things IMO for us to advance to the next age: near free energy (and more importantly for considerations such as this question) the ability to store, transport, and quickly discharge it.$\endgroup$
– MazuraJan 7 '19 at 0:24

I guess it is just for readers/viewers to be able to recognize in a fraction of a second that the character is holding a weapon that can hit at a distance.

To justify this would be so that military personnel doesn't need to adapt to a new way of fighting and can be even more efficient than before without the required formation time.
Then you still need batteries, plasma ammunition, electronics to handle the energy release, attachments and so on that make is as big as a classic gun.

$\begingroup$Not just the viewers - the first season or so of Star Trek: the Next Generation used less gun-like phasers (affectionately known as "dustbusters" for their shape) that had to be phased out, no pun intended, because the actors couldn't reliably point them at their targets.$\endgroup$
– CadenceJan 3 '19 at 16:16

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$\begingroup$The TNG phasers were my first thought when reading this. They weren't gun-like, and they failed. From the perspective of getting an audience to accept a fictional element, it's less of a jump to use something they recognize. Answers trying to justify the rifle shape of "laser guns" are all based on our current tech/cultural framework, anyways. Which is why it's important to clarify the question - are we asking "why do most fictional universes portray them this way?" or are we asking "what might they actually be like in a "realistic" future fictional universe?"$\endgroup$
– dwizumJan 3 '19 at 17:34

$\begingroup$@Cadence As a counterpoint, the hand weapons from Blake's 7 looked nothing like conventional guns, - see image here: therpf.com/forums/threads/blakes-7-prop-replicas.41273 but they sure looked easy enough to use in the show. One of the unintentionally unanswered questions from that show was any hint as to the nature of the former owners of the ship that Blake and his allies started using. Those weapons suggest that they might not have been completely anthropomorphic.$\endgroup$
– dgnuffJan 4 '19 at 3:24

$\begingroup$@dwizum I've never imagined the ST hand phaser as a primary weapon - it's all about the concealment. The Federation likes to appear peaceful and straightforward, and when their operative is caught, the phaser doesn't look like a weapon (we've even seen that on the show); it's designed not to look like a weapon. It's more like the single-shot concealed guns that used to be pretty popular for ladies, or something like a gun in your walking stick - not accurate at all, just something inconspicuous you can easily carry for emergencies. It also doubles as a tool, somewhat akin to a survival knife.$\endgroup$
– LuaanJan 5 '19 at 8:36

For a given level of technology a rifle has more space for "stuff" than a pistol.

What sort of stuff?

Power/energy: it can fire more times before it runs out of juice. It can also pack a greater punch for armour piercing.

Targeting: The rifle form factor allows invisible light sensors to read the eyes of the shooter and automatically place the laser on target. It also allows dynamic aiming adjustment to keep the shot on target long enough to be effective. I always thought Predator shoulder mounts have no way of targeting unless linked to a visor.

Robust/Hardened design: smaller form factors are more prone to failure of delicate parts. A laser that can't shoot is just a stick.

Heuristics/Learning curve. It's pretty obvious which end to point towards enemy and a trigger to activate. If it looked like a Dyson Airblade (or a makeup mirror, or a bow & arrow) it's not so obvious.

Alternate form factors

I believe we are in the last generation of personal war-fighting. Drones and automatons are the future.

So an adventuring rascal of the future is more likely to have a weapon drone in close proximity or close response time.

Yondu Udonta in Guardians of the Galaxy has his Yaka Arrow.

Han Solo should have wasted Greedo (first!) with a small remote sitting on the booth. Of course that would change the cowboy elements of the space opera.

Close protection drones would probably be big enough to shield behind while they lay fire upon aggressors. So I'm guessing the size of a riot shield.

If personal anti-gravity doesn't exist in your world then the drone has wheels and/or legs.

Another approach: the Close Protection Drone is actually made up of nano-robots hiding as clothing and cover exposed body parts quickly. Return fire is handled by specialised nano-bots that are part of the outfit and therefore have no specific form. Laser fire shoots out of the body.

The laser source is a long tube. The beam bounces back and forth in it and is amplified by the excited medium inside. The thinner and longer the tube is, the better collimated the beam is. That means it does not spread as much and therefore remains effective at longer distance.

The long barrel also makes aiming more accurate.

The stock is not needed to absorb recoil, but the additional fixed point it provides improves how steady you can hold it to get good aim.

$\begingroup$Also, the stock can house the heavier bits of the rifle (like the power supply) - this again makes it much easier to hold and aim the weapon, regardless of recoil. You want a heavy point near your body (which doesn't move much), and a relatively light end (that makes it easy to change the weapon's orientation).$\endgroup$
– LuaanJan 5 '19 at 8:39

$\begingroup$Point 1 is true for some lasers, but not semiconductor or fiber based lasers. Laser diodes are simply chips, and fiber lasers/amplifiers have the fiber rolled into a spool.$\endgroup$
– user71659Jan 5 '19 at 23:09

$\begingroup$@user71659, the aspect ratio of semiconductor and fiber lasers still determines their divergence. They are just very small generally in the first case, or allow not having the resonator straight in the second. Since the gain is limited by volume, you need something bigger for a gun anyway.$\endgroup$
– Jan HudecJan 7 '19 at 9:27

$\begingroup$Why would it? You've proposed an alternative, but you don't really discuss why that alternative would be the most likely. Can you Edit to elaborate on the reasoning behind your answer?$\endgroup$
– a CVnJan 3 '19 at 16:48

$\begingroup$this answers exactly the opposite question to the one posed.$\endgroup$
– thsJan 3 '19 at 19:09

$\begingroup$Why? Because there's nothing better than accelerating an actual mass at your enemy with e.g. a plasmacaster. Also, shoutout to Blue Thunder. "A real futuristic personal ' 'laser beam' ' weapon would probably" ... shoot bolts of plasma. And actually it would finally be back to looking like a (deck) 'gun' instead of a firearm.$\endgroup$
– MazuraJan 5 '19 at 22:18

$\begingroup$Luckily these must have about a 30 degree error correction, given some of the angles we've seen energy come out of them. It's going to need a selfie cam to know what you're looking at.$\endgroup$
– MazuraJan 5 '19 at 22:23

In addition to the excellent reason given by Daniel B, there are other considerations with the look, expectations and usability issues. Guns, like knifes or spears, have two ends, a good one and a bad one. If your laser gun looks like the Star Trek TNG class 1 phaser:
then you not only risk holding it the wrong way (darn it, which way to enemy?), but also it isn't clear to enemies what you are holding. What's that, a garage opener? A medical scanner?

For a gun, as famously pointed out by Douglas Adams, it is important to make sure that you know when you are at the wrong end of it. With a traditional gun design, there is no doubt. Bullets come out... here.

Makes me think of a fun detail I saw in "Edge of Tomorrow". A thing that looked like what I believe is called a "claymore" mine with "This side to enemy" written on one of its otherwise identically looking sides. I don't know whether these have that text written on them in reality, but I wouldn't be surprised! The design sucks ass.

Now that we come to design, why does a pistol look like a pistol, and why do little boys who play cowboy point out their index finger? Well, guess why. Because that's exactly what the design of a pistol imitates, and it is exactly what we are innately able to do without training. You can just point your finger at something, and your finger will point to it 99% good. There's no doubt about what pointing the barrel towards something in the same manner will do either.

There would be much "better" designs for pistols that transmit recoil more favorably. But they don't let you point your imaginary index finger intuitively.